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public class: FutureTask [javadoc | source]

All Implemented Interfaces:

Direct Known Subclasses:
    QueueingFuture, ScheduledFutureTask

A cancellable asynchronous computation. This class provides a base implementation of Future , with methods to start and cancel a computation, query to see if the computation is complete, and retrieve the result of the computation. The result can only be retrieved when the computation has completed; the get method will block if the computation has not yet completed. Once the computation has completed, the computation cannot be restarted or cancelled.

A FutureTask can be used to wrap a Callable or java.lang.Runnable object. Because FutureTask implements Runnable, a FutureTask can be submitted to an Executor for execution.

In addition to serving as a standalone class, this class provides protected functionality that may be useful when creating customized task classes.

 public FutureTask(Callable<V> callable) 
    Creates a FutureTask that will, upon running, execute the given Callable.
    callable - the callable task
    NullPointerException - if callable is null
 public FutureTask(Runnable runnable,
    V result) 
    Creates a FutureTask that will, upon running, execute the given Runnable, and arrange that get will return the given result on successful completion.
    runnable - the runnable task
    result - the result to return on successful completion. If you don't need a particular result, consider using constructions of the form: {@code Future f = new FutureTask(runnable, null)}
    NullPointerException - if runnable is null
Method from java.util.concurrent.FutureTask Summary:
cancel,   done,   get,   get,   isCancelled,   isDone,   run,   runAndReset,   set,   setException
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.util.concurrent.FutureTask Detail:
 public boolean cancel(boolean mayInterruptIfRunning) 
 protected  void done() 
    Protected method invoked when this task transitions to state isDone (whether normally or via cancellation). The default implementation does nothing. Subclasses may override this method to invoke completion callbacks or perform bookkeeping. Note that you can query status inside the implementation of this method to determine whether this task has been cancelled.
 public V get() throws InterruptedException, ExecutionException 
 public V get(long timeout,
    TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException 
 public boolean isCancelled() 
 public boolean isDone() 
 public  void run() 
    Sets this Future to the result of its computation unless it has been cancelled.
 protected boolean runAndReset() 
    Executes the computation without setting its result, and then resets this Future to initial state, failing to do so if the computation encounters an exception or is cancelled. This is designed for use with tasks that intrinsically execute more than once.
 protected  void set(V v) 
    Sets the result of this Future to the given value unless this future has already been set or has been cancelled. This method is invoked internally by the run method upon successful completion of the computation.
 protected  void setException(Throwable t) 
    Causes this future to report an ExecutionException with the given throwable as its cause, unless this Future has already been set or has been cancelled. This method is invoked internally by the run method upon failure of the computation.